It has been considered that by making surfaces of various substrates hydrophobic (water-repellency), adhesion of stain could be inhibited and good appearance could be maintained for a long period of time, and according to this way of thinking, surface treatment and coating as mentioned below have been carried out by using a fluorine-containing resin excellent in hydrophobic property (water-repellency).    (1) A method of adhering a fluorine-containing resin film to a substrate by thermal bonding (for example, JP8-132571A, JP6-155670A)    (2) A method of applying, on a substrate, a two-liquid curing type fluorine-containing resin composition containing an acrylic polymer as a stain-proofing coating agent (for example, JP3-275860A, JP2-299838A, JP2-299839A)    (3) A method of applying, on a substrate, a heat-meltable fluorine-containing resin composition containing vinylidene fluoride (for example, JP7-3220A, JP6-287334A, JP2-274534A)
In those surface treatments (1) to (3), highly hydrophobic fluorine-containing resins such as tetrafluoroethylene/ethylene copolymer and vinylidene fluoride polymer are used as a fluorine-containing resin to make a surface of a final product highly hydrophobic.
However, according to recent researches, it has been found that staining attributable to exhaust gases from cars and factories is caused by substances inherently having hydrophobic property (lipophilic property) and such lipophilic stain is easily adhered to a hydrophobic surface. Therefore, adhesion of lipophilic stain cannot be prevented by the above-mentioned surface treatments which only have a merit that the stain is easily removed by wiping with a cloth, etc.
There was a trial that a hydrophilic colloid was applied on one surface of a plastic film and another surface thereof was adhered to an outdoor article with an adhesive, thus making a surface of the article hydrophilic (for example, JP8-150681A). However, in this method, a formed hydrophilic surface layer is comparatively thin, and a long-lasting stain-proofing ability and stain-removable property cannot be obtained.
There are similar problems with respect to various products used in a damp site, for example, a sink of systemized kitchen unit, washstand, bath tub, drain pipe, etc. In those products used in a damp site, in many cases, stains are washed away with water by using a detergent or without using a detergent. If a surface thereof is hydrophobic, water-draining property is lowered and water remains in the form of water droplets and an organic substance in the droplets is adhered to the surface of the products as a fur in the form of line or spot. The fur not only lowers appearance of the product but also results in a slime due to propagation of bacteria. Those problems with draining around a damp site are also seen in various drain pipes.
Also there are many cases where fogging occurs on surfaces of various products due to moisture caused by a sudden change in temperature and humidity, and in some cases, prevention of such fogging is demanded strongly. For example, an acrylic resin board, polycarbonate resin board, hard vinyl chloride resin board, etc. which are excellent in transparency are used on a greenhouse, roof of carport, windows of building, etc. Also a film or sheet of soft vinyl chloride resin, polyolefin resin, polyester resin and fluorine-containing resin which are excellent in transparency is used on houses for agriculture in which sunlight has to be taken sufficiently. There is a case where fogging of various glasses, goggles, helmet shield and windows of airplane endangers a human life.
In order to prevent fogging of those board, film and sheet which require transparency, there have been proposed (1) a method of forming a resin mixture prepared by mixing a hydrophilic resin binder such as polymethyl methacrylate or polyvinyl pyrrolidone with an inorganic substance such as colloidal silica or alumina sol, into a board or a film, (2) a method of forming an anti-fogging surface layer by applying an anti-fogging agent comprising an unmodified polyvinyl alcohol and an inorganic substance such as colloidal silica or sodium silicate (for example, JP53-39347A, JP55-99987A, JP57-73059A) and (3) a method of forming an anti-fogging surface layer by applying an anti-fogging agent comprising a modified polyvinyl alcohol having a silyl group and ionic hydrophilic group in its molecule and an inorganic substance mainly on a glass plate or a polyester film (for example, JP59-179685A).
However in the method (1), anti-fogging property when fogging begins (initial anti-fogging property) is poor, and in the method (2), there are problems that wettability to water is insufficient and a surface hardness of a water-absorbed anti-fogging agent layer is lowered and therefore a flaw by scratching easily occurs. In the method (3), since an anti-fogging agent layer is adhered to a polyester substrate with an adhesive, there is a case where peeling of the anti-fogging agent layer arises depending on kind of an adhesive layer, and in addition, complicated production steps are required and cost is high.
Also there is a proposal of a method of forming, on at least one outermost layer of a plastic molded article, a coating film of a hydrophilizable coating composition containing an organometallic compound having a specific releasable group by hydrolysis (for example, JP2000-301054A), which indicates that adhesion of stain can be prevented by hydrophilizing a surface of the plastic article.
However those prior arts relate to a technology of imparting stain-proofing property for preventing adherence of stains by applying a coating composition to form, on a product surface, a coating film having a given strength or by adhering the film to the product surface.
Therefore for forming a coating film, after applying a coating composition, steps for vaporizing an organic solvent, drying and heating are necessary without fail.
On the other hand, there is known an easy method of applying and then wiping off a so-called wax composition to give a gloss on a surface of a substrate. A substantial difference between the wax composition and the coating composition is such that the coating composition is allowed to stand after coated to form a coating film (there is a case where forced drying is carried out but there is no case of touching the film) but in the case of the wax composition, a wiping-off step is necessary without fail after applying the wax composition and the wax component is rubbed on a surface of a substrate by a wiping-off force to adhere and form a wax layer.
In other words, a resin component for forming a film which dissolves in a solvent is essential for a coating composition, but in the case of the wax composition, such a film forming component is not necessary and rather obstructs steps for rubbing and wiping off the wax component. Adhesion of a formed wax layer to a substrate is obtained by wiping off the wax composition and the film of the wax composition itself is not formed into one continuous film unlike a coating film of coating composition. Even if the wax layer is a so-called continuous layer, it is not a film. Therefore though the coating film can be peeled in the form of film from the substrate, the wax layer cannot be peeled from the substrate as an independent film.
Since a wax composition has such characteristics as mentioned above, an effect of surface treatment with the wax composition does not continue long as compared with a coating film. The wax composition is used only as a glossing agent.
As a known wax composition, there is a glossing wax for cars. Some kinds of waxes for cars are endowed with stain-proofing property and wiping-off property in addition to glossing ability, and a component belonging to metal oxides is contained in some of wax compositions.
For example, JP7-196988A discloses a glossing agent comprising a silicone resin having hydroxyl or alkoxyl, wax component, organic or inorganic polishing material and further a solvent and silicone oil, and says that the glossing agent can provide a coating film surface having both of stain-proofing property and water repellency. This patent publication also says that a glossing agent having poor water repellency is relatively low in stain-proofing property.
JP11-21500A discloses a treating agent for a coating surface of car body which has good long-lasting water repellency and comprises a copolymer prepared by radical polymerization of an ethylenic monomer with a silicon compound having an unsaturated group and alkoxyl, organic solvent, wax component and silicone oil. This invention also says that water repellency of the coating film of the treating agent is essential. This patent publication explains that the same thing may be said with respect to many prior patent publications cited as prior arts in JP11-21500A (for example, JP62-132981A, JP4-363375A, JP61-246274A, JP50-157288A, JP1-163280A, JP7-41757A, JP7-109439A)
JP9-310046A discloses a glossing agent prepared by dissolving a wax component and silicone oil in an organic solvent by using a higher alcohol having alkoxyl as an emulsifying agent, optionally adding thereto a swellable layered compound for adjusting a viscosity and a resin component for fixing a coating film and then subjecting the mixture to emulsifying and dispersing in water. This glossing agent is also said to give water repellency and gloss and stain is said to be able to be eliminated when wiping off the glossing agent.
JP5-43840A and JP6-145600A disclose a surface treating agent for treating a coated surface which comprises a metal alkoxide or a polymer thereof, fluorine-containing silane compound, wax component, silicone oil and filler. In those patent publications, the surface treating agent is said to be able to maintain a long-lasting gloss and stain-proofing effect because the surface treating agent is chemically bonded to a coating surface. A coating film of this surface treating agent also has water repellency, and there was obtained a result that a stain-proofing effect is enhanced in the case of a high water repellency.
JP8-269401A and JP9-3408A disclose a glossing agent comprising a cured silicone rubber powder coated with hydrophobic inorganic powder, wax component, silicone oil and organic solvent, and say that adhesion of fur and dust can be prevented for a long period of time.
Any of those surface treating agents (glossing agents) containing a wax component make a treated surface hydrophilic and thereby enhance both of stain-proofing property and gloss.
Also JP8-60100A discloses that dispersions of aqueous solvents such as water and alcohols which contain a reaction product of colloidal silica with an organosilicate compound having 2 or 3 alkoxyl groups or a reaction product further reacted with melamine resin can impart a long-lasting gloss to surfaces of wood, synthetic leather, etc., can inhibit sliding property thereof and form the surfaces having excellent scrub resistance. This patent publication also discloses that a tetra-functional alkoxysilane such as tetraalkoxysilane may be added when preparing the reaction product and usual additives such as a wax component, silicone oil and metal powder may be added. However there is no teaching at all with respect to how to add water-repellent components such as wax component and silicone oil and what characteristics the obtained composition exhibits. What are disclosed therein are only aqueous glossing agents which are subjected to coating and impregnating without wiping off.
The present invention was completed as a result of unexpected finding that in a water-repellent surface-treating agent containing wax, when a specific hydrophilizing agent which can make a surface of substrate hydrophilic is added thereto, not only stain-proofing properties such as prevention of stain adhesion and stain removability are enhanced but also a glossing effect of the wax component is not lowered. Such a finding made a complete change in conventional way of thinking that water repellency is an essential point of a wax composition for exhibiting stain-proofing properties and glossing.
As mentioned above, it is known that a hydrolyzable organometallic compound is added to a coating composition comprising a resin as a binder to make an obtained coating film hydrophilic. In such a technology, a hydrophilizing effect can be exhibited when the coating composition is formed into a continuous coating film, and it has never been considered to apply such a technology to a treating agent not forming a coating film, particularly to a treating agent containing wax of which essential point has been considered to be water repellency.
An object of the present invention is to provide a hydrophilizable wax composition which can enhance and maintain stain-proofing properties without lowering gloss by adding a substance accelerating hydrophilization to a surface treating agent containing a wax.